When a printer for printing an object to be printed is started for printing or re-started after a color change or a version change is made, an amount of supply of ink tends to change and, as a result, surplus ink or blurring ink is adhered to the object to be printed and a normal product cannot be produced until a normal printing operation mode is brought about.
It has been practiced so far to supply a plurality of the same objects to be printed as a product during a period of time from starting or re-staring of the printer to starting of a normal printing operation and throw away these objects after printing.
In view of the fact that the objects to be printed which must be supplied and destroyed until starting of a normal printing operation amounts to a substantial number, Japanese Patent Application Laid-open Publication No. 9-123399 discloses a method for bringing about a normal printing operation without using an object to be printed which becomes a product.
According to this method, in an offset printer, an impression cylinder is separated from a blanket cylinder and an auxiliary roll is provided. This auxiliary roll is caused to contact the blanket cylinder and a part of ink which has been transferred to the blanket cylinder is transferred to the auxiliary roll. Then, this auxiliary roll is immersed in a solvent in a container, ink is wiped off with a wiping member and solvent adhering to the auxiliary roll is scraped off with a scraper. Then the auxiliary roll is caused to contact the blanket cylinder again. By repeating this operation several times before starting of printing, a normal printing state can be attained without using an object to be printed which becomes a product.
In this printing method, the operation in which ink transferred to the auxiliary roller is wiped off by immersing the auxiliary roller in a solvent and the solvent adhering to the auxiliary roller is scraped off is repeated is repeated for attaining a normal printing state but, as this operation is repeated, concentration of the ink in the solvent becomes gradually high and the wiping member is gradually soiled and, as a result, cleanliness of the auxiliary roll is deteriorated and it becomes difficult to attain a normal operation state under the same condition that a clean object to be printed which becomes a product is used.
Moreover, as printing speed increases, speed of rotation of the auxiliary roller also increases and there occurs the problem of scattering of the solvent and wiped off ink.
Furthermore, it is necessary to add a mechanism for vertically moving the impression cylinder of the printer itself and move the auxiliary roll with the container of the solvent and, as a result, the mechanism of the apparatus becomes complicated and bulky.